单选题 Some metals are better conductors of electricity than others,______ means that the former has atoms that contain more free electrons than the latter.
【正确答案】 D
【答案解析】本题考非限制性定语从句的用法。根据句意，故D项正确。本句大意为：一些金属比其他金属的导电性能要好。这说明前者的原子中比后者含有更多的自由电子。